Did we have a new eagle at the Decorah North nest last year?

Mom North rolling her egg

Hashtag this one #speculation! As Decorah North fans know, we had our first egg in that nest on March 11 in 2016. In 2017, first-egg timing retreated to February 19 - earlier than Mom and Dad Decorah! Why did it change so much?

Mom and Dad Decorah's first egg history looks like this:

• 2/18/16: First egg
• 2/18/15: First egg
• 2/23/14: First egg
• 2/17/12: First egg
• 2/23/11: First egg
• 2/25/10: First egg
• 3/02/09: First egg
• 3/08/08: First egg (note: this date is an estimation based on a photo of first hatch)

We know that Mom was laying for the first time in 2008. While we don't see a dramatic shift backwards, the first time she laid an egg also marked the latest time she laid an egg. Her nesting chronology slowly shifted earlier, yielding an average first-egg date on February 19 to date. 

Fort St. Vrain's first egg history looks like this:

• 02/14/17: First egg
• 02/16/17: First egg
• 02/14/15: First egg
• 02/21/14: First egg
• 02/17/13: First egg
• 02/16/12: First egg
• 02/16/11: First egg
• 02/14/10: First egg
• 02/17/09: First egg
• 02/27/08: First egg
• 03/03/07: First egg
• 02/17/06: First egg

Note that I didn't say Mom and Dad Fort St. Vrain's egg history. Looking at first egg dates, it appears we had a mate changeover in 2007, although we don't know whether it was Mom or Dad. As we saw in Decorah, nesting chronology slowly shifted earlier, yielding an average first lay date of February 15 to date.

How do peregrine falcons compare? Falcon nests experience a lot more turnover than any of the bald eagle nests we watch, making it difficult to develop data on partner nesting chronologies. For example, we've seen 11 mate changeovers in the 19 years we've banded at Xcel Energy's Blackdog plant in Eagan, MN. However, we can draw a couple of broad conclusions: 

• A change-over in the resident male or female falcon is often (but not always) accompanied by a change in nesting chronology. 
• Nesting chronology is somewhat more likely to move later in the first year of partnership and than move earlier as partners are paired over multiple years. 
• Return timing and territorial fighting both appear to influence nesting chronology, and territorial fighting is one factor in shifting egg-timing later. If a gravid female falcon is killed by an invading female falcon, the resident male will need to court her and fertilize her eggs, moving the nest's chronology later for at least the first year. 

A lot of people speculated that Dad North was new on site last year. While we don't know for sure, the remarkable shift in first egg timing indicates that one of the parents - possibly Dad North - was new. We don't know whether territorial interaction played a role, and we also don't know whether a new male could impact timing differently than a new female. But we will move egg-watch for Decorah North earlier next year. Will we also see a difference in parenting styles and outcomes in the North nest this year? We look forward to finding out!

Note: The Eagle Valley Eagles laid later in the one year we were able to watch them. I wish we could have had at least a few more years to take a look at their nesting chronologies as well, since some of their behavior and provisioning seemed more like what we experienced in the North Nest last year than in the Decorah nest since 2010.

Personalities

Filed under #musings. A recent study on animal personalities got me thinking. Are the differences we see from nest to nest a product of our imaginations, the surrounding area, or their personalities?

Between 2003 and 2015, we watched bald eagle families on four territories: Decorah and Decorah North in Iowa, Fort St. Vrain in Colorado, and Eagle Valley in Wisconsin. They were very similar in their broadest outlines, since all four territories:

• Were inhabited year-round by a territorial pair of eagles.
• Were close to bodies of water.
• Had distinctive seasons that included cold snowy winters, short unpredictable springs, and hot summers.
• Were near what appeared to be ample food supplies: the trout hatchery in Decorah; a river, watering hole, and prairie dog colony at Fort St. Vrain, a trout stream and farms at Decorah North, and the Mississippi river at Eagle Valley.

However, watchers of the Decorah and Decorah North nests observed some big differences between the two last year.

At Decorah
We have been collecting data on this territory since 2006, when Neil and Bob began filming American Bald Eagle. We don't know Dad's age, although he is older than Mom. Based on her barely-adult plumage when she began nesting here in 2007, she turned 13 in 2016. Both eagles are experienced parents.

• Both parents spent a lot of time on nestorations: bringing in sticks, arranging sticks, and moving sticks. 
• The 'pan-tree' was almost always full. It wasn't uncommon for the nest to contain four or five prey items - not surprising, since Dad was observed bringing in as many as five fish in one hour! 
• Both parents fed young on a regular basis. While Mom tended to take over feeding, Dad fed when he had a chance. The eaglets were fed together and separately. Human watchers believed that Mom and Dad tried to make sure both eaglets got sufficient food. 
• A parent - usually Mom but sometimes Dad - was always present in the nest until long after the eaglets could thermoregulate.
• The eaglets showed less aggression towards one another.
• Fish made up a larger part of the eagles' diet.
• Egg-laying started on February 18.

At Decorah North
We have been collecting data on these two eagles since February of 2016. We do not know how old either eagle is (although both appear to be full adults), how long they have been together prior to last fall, or how long they have been parenting.

• Less time was spent on all aspects of nestoration during the period we were able to watch both nests. Fewer sticks were brought in and the eagles spent less time moving and rearranging them.
• The parents did not cache nearly as much food in the nest. 'Field-dressed' prey was more commonly brought in than entire chunks or whole bodies that needed defurring or descaling.
• Young were not fed nearly as often and separate feedings were not as common. Human watchers believed that Mom and Dad did not try to allocate food evenly between the eaglets.
• Parents were not always present in the nest. Human watchers believed that they were more attuned to the brooding needs of the two older eaglets versus the youngest one.
• The eaglets showed a great deal of aggression towards one another. Sibling aggression was a factor in DN3's death.
• The prey base was wider and did not include as much fish as the Decorah nest - although based on a journal by Sherri Elliott, fish still comprised around 66% of their diet. It included opossum, muskrat, raccoon, fawn sections, rabbit, mink, cow placenta, birds, waterfowl, a cat, and unknown pieces of meat.
• Egg-laying started on March 11.
• The North Nest had more nest intruders and slightly harsher weather.

At the time, we believed that the difference in parenting styles was driven primarily by food availability at each nest. Since the Norths brought less food into the nest, it made sense that less food might be available overall, and their relative absence could be explained by the need to spend more time hunting. Food was also clearly a big factor in eaglet aggression, which tended to determine who was fed first or at all.  Our conclusions were consistent with earlier studies of bald eagles conducted at Besnard Lake, in Alaska, and on Chesapeake Bay. You don't have to watch eagles very long to realize how important food is. But could eagle coping styles/personalities also be playing a role? 

Let's start with defining the term 'copying style'. Jaap Koolhaus (Koolhaas et al. 1999, 2010) describes a coping style as a correlated set of individual behavioral and physiological characteristics consistent over time and across situations. Researchers divide coping styles into proactive and reactive groups:

• Proactive individuals respond to stressful situations with action. They build rigid routines, explore territories quickly, develop superficial maps, tend to be offensive towards conspecific rivals, are impulsive in decision-making, score high in frustration tests, take risks in the face of potential dangers, and are novelty seekers. Perhaps as a result of their routines, they are less responsive to short-term changes in their environment. 
• Reactive individuals respond to stressful situations with immobility. They are less likely to build rigid routines, explore territories slowly, develop deeper maps, and tend to be less offensive towards conspecific rivals. Perhaps as a result of their flexibility, they are more responsive to short-term changes in their environment. 

So how might behavioral type affect local space use in bald eagles? Unsurprisingly, it is a complex question. As defined above, the North adults seem proactive (quick, active, aggressive, less responsive to environmental changes and external stimuli) and the Decorah adults seem reactive (slower, less active, possessing a deep understanding of the territory, very responsive to environmental changes and external stimuli). One of the things that watchers commented on was the absence of Mom and Dad North when compared to Mom and Dad Decorah. Several studies have found that proactive individuals show a wider ranging space use than their reactive counterparts. The North eagles spent less time in the nest and on the nesting tree last year. Was that driven only by food availability or did a deep-seated need to range also play a part? We also discussed the differences in parenting styles quite a bit. The Decorah eagles seemed to human watchers to be much more reactive to the needs and behaviors of their eaglets than did the Norths. Did personality have anything to do with it? 

A lot of the narrative around both eagle families seems to fit nicely into a proactive/reactive box. But what about prey piling and nestoration? Watchers identified prey piling as a big difference between the two families. The Decorah eagles piled prey high (and have ever since we began watching them), while the North eagles seldom cached prey in the nest (although left-over turkey feathers piled up, they didn't make a meal). Similarly, the Decorah eagles spent a lot of time working on their nest (Dad's sticky OCD, anyone?) when compared to the North eagles. These seem like rigid behaviors, not flexible responses to the environment, which puts them firmly in the proactive category. It could be argued that, unlike the Decorah eagles, the Norths didn't flexibly respond to changes in their environment (eaglets) with changes in their behavior (caching prey). However we categorize their behavior, both pairs of eagles appear to be using environmental information in different ways.

It hasn't been that long since it was taboo to think of animals as anything other than clinical study subjects. Changes in our way of thinking and advancements in research and study techniques have altered that. I am firmly convinced that personality plays a part in the unique behaviors seen at each nest (although food remains important) and I am looking forward to more research on the topic.

Note 1: Dana Bove of the Boulder County Audubon contacted us about bald eagle monitoring. He developed an Excel worksheet to monitor nests outside of the active reproductive period, i.e., when eagles may be in and around the nest, but aren't productively copulating, laying eggs, incubating, or caring for young. We were very interested in them given the differences in the Decorah and Decorah North nests. How big were those differences in behavior? We received permission to use his protocol and put it online here. Please feel welcome to start sharing your observations via the tool. This is a bit of an experiment for us, so feel welcome to share feedback as well!

Note 2: Some watchers believe that parental experience also played a role. Like many animals, eagles get better at basic parenting skills with experience. Could some of the differences in preparation and provisioning also be a matter of an experienced parent at the North Nest?

Note 3: Could nest invaders be another piece of the puzzle? Eagles enthusiastically steal prey from one another and hungry hawks will sometimes invade as well. Could the difference in prey piling and preparation be in part a response to potential competition and nest invasion? A lot to think about!

---

We see proactive and reactive behaviors in nesting peregrine falcons when we handle them for banding. Some falcons foot and bite the entire time, while others are very docile and don't put up a struggle at all. A few observations...note that these are anecdotal:

• Highly aggressive females seem to replace highly aggressive females. I can think of at least three sites where female falcons were dangerously aggressive. We've never had anything but dangerously aggressive falcons at those sites. 
• There is a general belief that highly aggressive falcons produce highly aggressive offspring, although to my knowledge it has never been formally studied.
• Footy, bitey males tend to be older than female siblings based on plumage growth. 

A study on crows found that dominance-related parameters of age and sex did not coincide with proactivity. I wondered about this since older, bigger eaglets tend to be more dominant, and older nestling falcons are more likely to be aggressive when handled. In effect, a study on this would be looking at whether birth order influenced personality/coping strategies. We plan to start assessing docility in nestling falcons next year for comparison with their behavior should they survive to adults. We will also keep notes on dispersal - so keep those band numbers coming!

References

• Deventer, S. A., Uhl, F., Bugnyar, T., Miller, R., Fitch, W. T., Schiestl, M., Ringler, M. and Schwab, C. (2016), Behavioural Type Affects Space Use in a Wild Population of Crows (Corvus corone). Ethology, 122: 881–891. doi:10.1111/eth.12536
• Personality predicts spatial responses to food manipulations in free-ranging great tits (Parus major). Thijs van Overveld, Erik Matthysen Biol. Lett. 2010 6 187-190; DOI: 10.1098/rsbl.2009.0764. Published 12 March 2010
• Dingemanse, N. J., Both, C., van Noordwijk, A. J., Rutten, A. L. & Drent, P. J. 2003: Natal dispersal and personalities in great tits (Parus major). Proc R Soc Biol Sci Ser B 270, 741—747. Those of you have have followed eagle tracking might find this interesting: http://rspb.royalsocietypublishing.org/content/royprsb/270/1516/741.full.pdf
• Koolhaas, J. M., Korte, S. M., De Boer, S. F., Van Der Vegt, B. J., Van Reenen, C. G., Hopster, H., De Jong, I. C., Ruis, M. A. W. & Blokhuis, H. J. 1999: Coping styles in animals: current status in behavior and stress-physiology. Neurosci. Biobehav. Rev. 23, 925—935. Read here:
  http://www.rug.nl/research/portal/files/6658965/1999NeurosciBiobehavRevKoolhaas.pdf

Eaglet Growth and Development: Week Two

D24 and D25: 04/04/16

D24 and D25: 04/12/16

D24 is 15 days old today, while D25 turns 13 days old. The week-old difference between these two photos is striking. In their second week of development, the eaglets grew larger, gaining roughly two pounds between April 4th and April 12th. They experienced rapid growth in features like beaks, culmens, and footpads, replaced their white natal down with thicker grey thermal down, and began exploring the nest. Although they aren't yet standing on their toes, they are able to sit up - way up! - for feeding and shuffle around on their metatarsi.  Their eyes are wide open and fit more comfortably in their eyesockets, features like brow ridges are beginning to appear, and their legs and footpads are yellow, not pink. 

Gary Bortolotti wrote that bald eagles might gain more weight per day than any other north American bird, although the majority of their weight gain occurs within the first 30-40 days. This rapid weight growth is fueled by their nutrient-rich diet of meat. Over the past week or so, we watched the eaglets chow down on fish, roe (fish eggs), venison (aborted fetal deer), rabbit, squirrel, something that might have been a muskrat, waterfowl, and several other birds. D24 became proficient enough at shooting poop to christen the Poopcasso tree on April 5th, while both eaglets got in plenty of tussling and bonking play, alternately hitting, submitting, and quitting to cuddle in the nest cup, grow, and wait for more food to arrive.

Watchers have been asking why the Fort St. Vrain eaglets began wandering the nest so much earlier than the Decorah eaglets. While we don't know for sure, we suspect that temperature played an important role. Fort St. Vrain experienced unusually warm temperatures in late March and early April, and the leaves hadn't unfurled to provide shade for the nest. Cold is a challenge to eaglets under 10-15 days of age, but so is heat! With little ability to control body temperature and no way to lose heat except by panting, the eaglets did their best to retire to what little shade tree limbs and the nest itself offered. Once in the shade, they sprawled out as much as they could. Mom did her best to provide shade for the eaglets, moving from one to another and standing between them and the sun.  As alarming as it was to viewers, Mom's ploy worked and we didn't see quite as much wandering, at least for a few days, after the weather cooled down. 

In the week to come, we can expect (continued) rapid growth in footpads, talons, and legs. Beak growth will rapidly slow as the eaglets' beaks approach adult size and we may see dark juvenile feathers start to sprout from their grey down. Overall weight and height gain will continue, most  likely reaching their steepest curves some time this week. By the end of the week, our little bobbleheads at Decorah and Fort St. Vrain will be almost a foot tall, while the eggs at Decorah North should begin hatching! 

Watchers have observed that different nests seem to have different 'parenting' styles: i.e., Dad may be more present at one nest than another, food may come in more or less regularly, and eaglets might spend more time alone. Many things influence nest life, including weather, temperature, food availability, predators, and the presence of other adult, sub-adult, and juvenile bald eagles. While eaglet growth and development occurs along a fairly predictable trajectory, local conditions can change the timing of events - something we've seen in Decorah, Fort St. Vrain, and the year we watched Eagle Valley. We are looking forward to hatch at Decorah North!

---

The general stages of eagle development are:

Stage 1 - Structural growth. In their first thirty-five to forty days of life, eagles grow very rapidly, gaining weight and building bones, muscles, tissue, and features like tarsi, footpads, toes, and claws. This phase of development slows down about halfway through an eaglet's time in the nest, even though individual features might continue some level of growth.

Stage 2 - Feather and flight-related growth. Eagles grow four sets of feathers - natal down inside the egg, thermal down, juvenile feathers, and adult feathers. Thermal down starts growing at about ten days, juvenile deck feathers at about 20-23 days and juvenile flight feathers at about 27 days, but feather growth doesn't overtake structural growth until thirty-five to forty days after hatch. Flight muscles also begin growing as eaglets wingercize, flap, hover, and eventually branch and fledge.

Stage 3 - Neurological Coordination. Eagle watchers know how ungainly eaglets can seem! As they grow, they become more adept at controlling beaks, legs, wings, and feet. They learn to stand on their own feet, tear food, self-feed, and flap their wings, going from cute but clumsy clown clompers to graceful young eaglets poised at the edge of fledge.

I'm not sure how familiar many of you are with the cortical homunculus, an image-based tool that maps tactility. We discussed it very briefly in this blog and I'll include links below. While useful and extremely cool, most cortical homunculii are static - that is, they reflect just one phase (usually adult) of an organism's life. But an eaglet's cortical homunculus will differ from an adult's as body parts and associated skills are gained and neural pathways developed. Our eaglets' brains and bodies are rapidly growing and changing as they gain the skills they need for life outside the egg! I'd tend to think that visual acuity suddenly 'lit up' this week, leading changes in coordination as the eaglets began sitting up and moving around.

Things that helped me write this blog, with a few considerations:

• Eaglet hatch weight is based on Gary Bortolotti's work with eaglets at Besnard Lake in Canada. It is possible that our eaglets are a little smaller than his, since Bald eagles get bigger the farther north one travels: a phenomena known as Bergmann's Rule. Bortolotti's paper makes for interesting reading and provides a great look at the work involved in field science. Citation: Physical Development of Nestling Bald Eagles with Emphasis on the Timing of Growth Events, The Wilson Bulletin, Vol. 96, No. 4 (Dec., 1984), pp. 524-54.https://www.usask.ca/biology/bortolotti/pubs/wb96-4-524-542.pdf
• Mouseunculus:http://phenomena.nationalgeographic.com/2013/07/24/mouseunculus-how-the-brain-draws-a-little-you/
• Homunculus: http://io9.com/5670064/how-your-brain-sees-your-body-meet-the-cortical-homunculus
• Input from Bob Anderson, who imparted much wisdom and information before he passed.
• RRP moderators and their calendars, lists, books, charts, and personal observations.

Sounds of the Eagles

I just finished the book Birdsong by Don Stap, a book which seeks to answer the question Why do birds sing and what do their songs mean? Most studies of bird song have been done on oscine birds, which are a subset of passeriformes with a complex voicebox. Many oscine birds such as chestnut-sided warbler, brown thrashers, hermit thrushes, and starlings sing complex sounds that might include, depending on the bird, buzzing, clicking, trilling, and warbling. Non-oscine birds like bald eagles (an accipitriform) might fascinate us with their striking colors, amazing flights, and sheer size, but their vocalizations don't tend to overwhelm us with their beauty or musicality.

After reading Birdsong, I decided to download some spectrogram software and run a few eagle vocalizations through it. The software I chose was Praat, a powerful free acoustical analysis program available from the University of Amsterdam. I wanted to see how 'questionable' copulatory vocals (are they mating?) appeared next to known copulatory vocals (they are mating!).

This was the sort of thing I tended to see. Copulation followed a pretty clear pattern, and Dad also tends to have a higher voice than Mom as shown by the sonograms above. 'Was that copulation?' is Mom alone and was not, in fact, copulation: the bars are low (signaling Mom's deeper voice), thick, and pretty distinct. 'That was copulation!' starts with a brief vocal by Mom at left, and continues into Dad's copulatory vocals - high, quick, and a little complex.

Did all eagle vocals look somewhat like copulation? While Dad's copulatory vocals tend to have a unique sound (I listen for a little warble or chirp and count to seven), eagles don't have complex voiceboxes, and the top vocal isn't that different from the bottom vocal. I decided to compare known non-copulatory vocals next.

Look at 'Mom with a Fish'. It was a cool sounding vocalization and doesn't really look much like copulation. If anything, her initial vocalizations look a lot like Dad's in the 'Sound a Warning' spectrogram , although they are lower. She was mantling a fish after what sounded like a couple of warning vocalizations before she came to the nest, and concentrated energy in high and low pitches, just like Dad did with his initial warning to an unknown neighborhood intruder. The second part of 'Sound a Warning' features Mom and Dad rapidly vocalizing together. While this somewhat resembles the 'solicitation' spectrogram, the vocal pulses are a little farther apart and higher. Personally, I think that 'Mom solicits Dad' most closely resembles copulation. Is she vocalizing the 'music of love' to indicate receptivity? Note that the unknown noise in the spectrogram figure prior to this one really closely resembles her solicitation.

Of course, I also had to compare known copulations. Keep in mind that we used different microphones in 2012 than we do now, and they were located in a slightly different position relative to the nest.

Even given the changes since 2012, these spectrograms look quite similar! It appears that copulatory vocalizations are quite distinct, and spectrograms could be used to help determine whether those early to mid-January vocals are copulatory in nature. After all, we can't always see what Mom and Dad are doing in the upper branches!

While this was more of a thought experiment than anything else, it looks like bald eagles have a little more to say than we realize, even if they aren't singing when they do it. I am looking forward to recording their interactions with eaglets later this year.

---

I am not a sound recordist. I am sure these spectrograms would benefit from professional equipment, but I have a 64-bit ASUS PC laptop with no special audio equipment whatsoever. The spectrograms were made recording youtube videos via praat in the quietest room of my house, with no one home except myself and two dogs. They were taken from the following videos (note: I can't find the 'was that copulation?' from 2016):

• 1/23/16: Mom and Dad vocalize a warning: https://youtu.be/K-vbdafsuro
• 01/28/16: Mom with fish, vocalizes warning: https://youtu.be/jjWx994INUg
• 01/27/16: Dad with fish, breakfast squabble: https://youtu.be/zum0p7JjnOc
• 1/31/16: Mom wants Dad: https://youtu.be/wR06cBSlj80
• 1/30/16: Sounds like mating on branch with shadow on nest: https://youtu.be/soH7wWAfXZc
• 2/14/12: Decorah eagles mating and vocalizing: https://youtu.be/XH6Zdp9l2mc
• 2/15/12: Decorah eagles mating: https://youtu.be/r8ESXahkLg8
• 2/03/12: Decorah eagles mating: https://youtu.be/z9K-EOigbSg

Book: Birdsong - http://smile.amazon.com/Birdsong-Don-Stap/dp/1451612974/

Praat audio software: http://www.fon.hum.uva.nl/praat/

Birds and Nest-Building

This blog was inspired by the paper 'The design and function of birds' nests', Ecology and Evolution 2014; 4(20): 3909–3928. It can be found here: http://bit.ly/1Q55LZd

Hard at work on N2B

What determines the design of a bird's nest? You know the type of nest I'm talking about, right? A bald eagle's large platform nest, built with sticks, high up in the branches of a tree.  Or maybe a scrape created in dirt or gravel on a shallow cliff ledge by nesting peregrine falcons. How about the burrows created by bank swallows and belted kingfishers, or the cavity nests excavated in trees by woodpeckers? Or am I thinking of the pendulant and sometimes very elaborate suspended nests created by orioles and weavers?

When I think of bird nests, I think of the classic small cupped nests I collected as a child. But birds nest in a variety of ways and places, creating nests from twigs, sticks, moss, grass, fur or hair, roots, bark, leaves, pine needles, feathers, lichens, paper, insect cocoons, snakeskin, saliva, and other materials. They nest high in trees, but they also nest on the ground, under the ground, in the darkness of chimneys and caves, and even in active wasp nests. Some birds construct elaborate nests while others get by with a shallow scrape in a stolen or abandoned nest.

Nests traditionally have been thought of as nothing more than places for birds to lay eggs and raise young. It was assumed that natural selection and the need to minimize the risk of predation determined the design of completed nests. However, recent research has found that sexual selection, parasites, and the need to build a nest that can handle variation in weather conditions (which we certainly see in Iowa, Colorado, and Minnesota!) also play significant roles in influencing nest design.

Sexual Selection
How does sexual selection play a role in nest design? It goes something like this: birds that build awesome nests relative to other members of their species must be healthy, high-quality mates. Think about Decorah. Mom and Dad spend a lot of time procuring and hauling wood and soft materials into the nest. This is a costly activity energetically speaking, and it requires both eagles to be in good shape - well-fed (which implies provisioning ability), skilled at flying, and relatively parasite-free. While different things might indicate quality to different species of birds, it appears that large nests signify quality among bald eagles.

Bald eagle nests are bi-parentally built - that is, both parents work on them. However, in Decorah it is Dad who spends the most time getting the sticks just right, scraping in the nest bowl, and preparing the egg cup. Studies have found that female magpies adjust their reproductive effort in relation to the male's nest-building activities. The more time he spends working on the nest, the more time and energy she puts toward reproductive processes, including copulation.

What could we watch for in our eagles? A study of male house sparrows found that they call to females when adding feathers to the nest, suggesting that they wish the behavior to be observed. The volume of feathers delivered by males was positively correlated with clutch size and female provisioning rates. While Dad doesn't usually vocalize when he places a stick, he often interacts with Mom in some way - taking a stick from her, moving sticks while she is in the nest, and so on. His obsession with proper placement might be his way of signaling fitness and getting more tailfeather from Mom to boot! I'm going to pay more attention to Mom and Dad's interactions during and following their sticky adventures!

While the paper doesn't touch on intelligence, it is hard for me to believe that it isn't part of the total sexual selection package. Building a nest is a lot harder than it looks and requires a whole host of things: access to food (which implies hunting ability and understanding of a territory, among other things), strength (which implies access to food and a body relatively free of parasites), and flight skills (ditto). An intelligent bird will presumably make better decisions about maximizing energy gain, procuring food, and hauling and placing sticks. Its intelligence should help it live longer and build a sexier nest, which in theory will lead to more copulation, more fertilized eggs, and offspring that inherit Mom and Dad's traits.

Parasites
Bird parasites include lice, fleas, flies, mites, ticks, leeches, fungi, and bacteria. We've seen firsthand the damage that blackflies and hippoboscids can do: killing young falcons, driving young from the nest to early, and delaying development. Birds have a wide variety of responses to parasites, including molting feathers, the use of feather toxins, preening, and maintaining their nests.

Watchers might remember Stitch and Spot, the red-tailed hawks from Eaglecrest Wildlife. Male Spot brought green plant material into the nest on a regular basis. The greenery (probably blue oak branches) contained high levels of monoterpenes and isoprene, which helped reduce parasites and fungi and may also have signaled fitness to female Stitch in the same way that a large nest might signal quality to a female eagle [a blog on greenery and parasites can be found here].

However, the bald eagles we watch don't appear to intentionally carry greenery into their nests. So what do they do? Many watchers have commented on the number of mice in the nest. For the mice, an eagle's nest offers food (scraps of protein and stomach and crop contents of prey), shelter, and safety from serious mouse predators like fox and owls. While bald eagles would eat a mouse, it isn't much more than an hors d'oeuvres compared to prey like pigeons, trout, squirrels, and so on, so the risk is well worth the payout! In return, mice devour leftovers and help keep the nest a little cleaner and presumably parasite-free than it would be otherwise. As with greenery and hawks, sexual selection might drive a nest-building behavior that also repels undesired guests!

An early nesting season also helps reduce parasitization of young, although it means parent birds need to be ready for the challenges that winter brings. This leads us to...

Environmental Adjustment
Remember 2013? The birds we watch produced young in the teeth of the worst winter since the 1970s. Our eagles were successful in part because the design of their nest influences the microclimate in which eggs and young are incubated. Dad's attention to the nest bowl - rolling, scraping, nest digging, and the careful arrangement of soft materials to form a cup once the substrate is suitable - may both excite Mom and result in a structure that can weather rain, snow, and serious sub-zero temperatures. Of course, if you watch the eagles, you have probably already realized that the types and placement of materials aren't accidental. We've seen the nest bowl and cup carefully prepared ahead of time, and we've seen Dad bring grasses and husks to tuck around Mom while she incubates eggs.

So the next time you watch a bird build a nest, either online or off, remember that much more is going on than meets the eye. Sexual attraction, courtship and flirtation, proof of fitness, and protection of young from parasites and weather all appear to play important roles in the design of finished nests.

---

Things that helped me learn and write about this topic:

• Paper: The design and function of birds' nests', Ecology and Evolution 2014; 4(20): 3909–3928. It can be found here: http://bit.ly/1Q55LZd
• The classification of bird's nests. There are a number of resources, but I thought this one was fun: http://www.backyardnature.net/birdnest.htm
• The 16 most amazing bird nests: http://www.bbc.com/earth/story/20150307-the-16-most-amazing-bird-nests

Did you know that?

There is a bird that nests inside a wasp's nest! Follow this link to read more about the Violaceous Trogon and its extreme housing practices!

Where do falcons and eagles go in winter?

Lately I've been getting asked where our falcons go to winter. The answer is complex. Birds do not fly south simply to escape the cold. Snow and ice seal the food supply and/or habitat of many birds away until spring: hummingbirds don't have flowers, waterfowl don't have water, and most insectivores don't have insects. However, peregrine falcons and bald eagles are able to weather winter since their food supply remains locally abundant, or at least present, year-round. Both species are partial migrators: that is, some birds migrate and others don't.

Bald eagles eat a wide variety of food, including other birds, mammals, reptiles, and invertebrates. They take their food live, freshly killed, frozen and left in the nest, or as carrion, and they can gorge food quickly and fast for days if need be. Peregrine falcons eat almost solely other birds they catch in flight, but many birds winter in Minnesota and Iowa, especially in cities and along open stretches of water. While there has historically been some natural open water along the Mississippi river during the winter (Eagle Valley, for example), the number of open water spots has increased with industrialization. Power plants discharge warm water that keeps stretches of rivers and lakes ice-free, providing spots for birds like swans and geese to winter (especially when people feed them, as they do here). Cities and industrial sites provide food and shelter for non-migratory birds like rock doves, which builds populations and makes wintering in place much easier. Even in the harshest winter, falcons and eagles have ample access to food in places like Minneapolis, St. Paul, Bayport, Decorah, Red Wing, and even northerly Duluth. 

Even with ample access to food, our winter weather is pretty gnarly. Birds have wings, so why don't they leave? We don't know for sure, but we do know that migration is costly and risky, and a good territory is hard to find. Falcons and eagles that stay on site have an advantage against territorial interlopers and are less likely to find themselves replaced by another mate come springtime. Years of occupancy on site yield a deep map of the the territory - places to find food, niches to shelter, and a knowledge of the local fauna - that helps animals survive even under adverse conditions (see this blog for more information about how eagles handle winter). 

So I've talked about peregrines and eagles that stay, but what about peregrines and eagles that leave? Transmitter studies indicate that mates don't migrate or spend time together off their breeding grounds. Among falcons and eagles, young don't migrate with parents, and we don't think they spend much time together after they disperse. 

Bald eagles tolerate - maybe even like? - cold. Many eagles that migrate don't fly into latitudes free of ice and snow. Eagles in central Canada might shift south as far as the Mississippi river in Minnesota, Iowa, and Wisconsin. Alaskan eagles go west to the sea. Eagles in central north America might fly to an open body of water not too distant from their breeding grounds, joining winter eagle congregations in places like Eagle Valley, Wisconsin; Clinton, Iowa (Eagle Point Park); Bayport, Minnesota (south of Xcel Energy's Allen S. King plant); and many other places.

Peregrine Falcon Migration Map

Peregrine falcons have been documented traveling a bit further south. We've had band returns from south Florida, an oil rig in the Gulf of Mexico, and Costa Rica (click these links to read about Island Girl and Immaculata). Thousands of Tundra peregrines have been trapped and banded at the Padre Islands in south Texas as they fly from an area up above the arctic circle to Central and South America - a distance of up to 15,500 miles! Florida reported a world record number of migrating peregrines just last week - an amazing 1506 in a single day count! 

In short, migratory eagles from Minnesota, Iowa, and Wisconsin might easily be wintering fairly close to home, spending time on open stretches of water along large rivers with eagles from central Canada who flew several hundred or a few thousand miles to get there. D1, D14, and Four all wintered in NE Iowa and (in D1's case) SE Minnesota (explore the cluster map for details). However, peregrine falcons from the same area might fly thousands of miles south to warm their feathers in Central and South America before returning to our area in late February and early March. 

The whole question of photoperiod length becomes even more interesting when migration is factored in. In late February, our latitude gets around 11 hours of sunlight daily. We peak on June 21, at 15 hours, 36 minutes. Non-migratory birds and Canadian migrants to our area also experience the shortest day, at 8 hours and 46 minutes on December 21. Falcons that migrate to Costa Rica experience a different photo-year than their non-migratory counterparts, however. A falcon that left on October 1 has a shortest day-length of around 11 hours. Its days will get slightly longer as it wings south. The shortest day in October in Costa Rica is 11 hours and 46 minutes long. The shortest day of the year is 11 hours and 32 minutes long. These birds have more average daylight over the course of the year, and a much flatter photo period map during the time they spend near the equator. The difference is even greater for birds like the Tundrius falcon, which summers at and above the arctic circle.

Some things that helped me write this post: 

• Mandernack satellite telemetry study: http://www.bioone.org/doi/abs/10.3356/JRR-10-77.1
• The Peregrine Falcon Research Group study: http://www.frg.org/SC_PEFA.htm
• Time and Date: http://www.timeanddate.com/

Canada Goose Update

The goose and the hawk. Hawks drive the
intruder from their nest.

In the last blog, I speculated that Wilma's nest intruder could have been dumping eggs. It looks like she dumped not one, but two! From Eaglecrest:

Canada goose Mom Wilma is incubating NINE EGGS...seven of her own and two laid right in her nest by a female intruder. The two "foreign" eggs were laid on 3-15 and 3-22. In both cases, Wilma relentlessly attacked the intruding goose until she left. We may not have seen the last of her. The two intruder eggs will not hatch with Wilma's...they are eleven days or more behind schedule. Wilma began full time incubation of her SEVEN eggs on Tuesday, March 4th. We will expect the little goslings to hatch around March 31st...with the "big jump" about April 1st. Mate Fred is in constant protection mode, as usual.

We've been asked why this goose is behaving so strangely. Why is she dumping eggs? Why is she trying to sit in a hawk nest? I'm speculating that our invader is responding to the recent death of her mate. I haven't seen her accompanied by a male, which is extremely uncommon. Mated male geese are almost always hovering around their nesting mates, protecting them from predators and other geese. A study done at Horicon March in 1959 indicated that reduced breeding productivity was almost entirely connected with goosey social behavior. The authors of the paper wrote: 

"Over half the birds assumed to be capable of breeding failed to make nests in which they laid and incubated eggs; one-fifth of the birds failed even to pair up effectively. The nine pairs that failed to lay eggs in nests were involved in unusually frequent territorial clashes, and most of them were unable to maintain stable territories for any length of time. Four of the 5 pairs (and perhaps all 5) that lost their clutches did so because of disturbance to the female from other geese, related to a lack of effective male defense."

So our unknown intruder doesn't have a male to help safeguard her nest from other geese, who can be very disruptive to laying and sitting. What seems like erratic behavior is really an attempt to produce young under extremely difficult circumstances. While the intruder's eggs won't survive this spring, she'll most likely pair up with a new male goose to try again in 2015. There is no shortage of geese at Eaglecrest!

Geese have an elaborate, shifting hierarchy ruled by ganders with large families. I'll write a little more about the importance of family once the eggs start hatching. To watch Eaglecrest live, go to http://www.ustream.tv/eaglecresthawks. We anticipate hatch in Wilma's nest at the end of March or very early in April. 

---

Resources

Social Behavior and Breeding Success in Canada Geese (Branta canadensis) Confined under Semi-Natural Conditions
Nicholas E. Collias and Laurence R. Jahn
The Auk
Vol. 76, No. 4 (Oct., 1959), pp. 478-509
Published by: University of California Press
Article Stable URL: http://www.jstor.org/stable/4082315

Some of what we're seeing could also be a response to crowding, which impacts reproductive and social behavior. As California's drought reduces water resources, birds and other animals crowd more densely around those that remain. We'll explore the impact of crowding in a future blog.

Red-Tailed Hawks and Social Play

Eaglecrest facilitator mochamamma has captured several videos of young red-tailed hawks squabbling, chasing, and stealing food from one another.

• Eaglecrest live stream: http://www.ustream.tv/eaglecresthawks
• Red-tailed hawks fight and chase: http://www.youtube.com/watch?v=xpL_4_xfdnI&feature=share&list=PLeNR2ocnlCOe1ME2oM1i-ixbUGV03AGiF
• Five hawks: http://www.youtube.com/watch?v=mxVug0Ackjc&feature=share&list=PLeNR2ocnlCOe1ME2oM1i-ixbUGV03AGiF
• Eight hawks: http://www.youtube.com/watch?v=XMijoLfGq-o&feature=share&list=PLeNR2ocnlCOe1ME2oM1i-ixbUGV03AGiF

At first we thought they might be nest mates – although Stitch and Spot hatched just one young hawk, there are other nests in the area. But as the hawks piled up – three, four, five, eight – it became increasingly clear they weren’t related. What was going on?

We had a couple of ideas. Eaglecrest’s pond is a hot spot for local wildlife. Well over 30 species of animals have been captured on camera, including reptiles, amphibians, several mammals, and many birds. Large concentrations of raptors have been recorded at watering holes in Africa, Australia, the American Southwest, and other arid places. The young hawks at Eaglecrest were probably drawn in from the surrounding area by the pond’s abundant food and water supplies. But are they competing for limited resources or engaging in play and social interaction? Maybe a bit of both is happening.

I tend to think of red-tailed hawks as fairly solitary creatures. They chose a mate, build a nest, and defend their territory from interlopers, including other red-tailed hawks. But researcher Charles Preston observed red-tailed hawks in winter communal roosts of four to six members. These roosts sometimes included ferruginous hawks and at least one was close to a large communal roost of bald eagles.  Red-tailed hawks will also concentrate in higher numbers based on prey availability, which is probably why I start noticing them in larger numbers mid-fall. Like many other birds, red-tailed hawks are far less territorial when they aren’t breeding, although it might be a stretch to call them social. Yet juvenile red-tailed hawks engage in social play.

Play is well-documented among juvenile red-tailed hawks. They have been observed playing with inanimate objects like rocks and sticks – stalking them on the ground, pouncing on them, and dropping and catching them in flight. Play seems to have evolved in most species that provide prolonged periods of parental care, and red-tailed hawks are no exception. As Charles Preston notes, the young birds “may gradually broaden their range of hunting methods and increase their skills by learning from their parents or other red-tailed hawks.”

The young red-tailed hawks at Eaglecrest chase one another, steal prey, and mock fight. They spread their wings, assume striking poses, mantle food, stalk through the undergrowth, and wrestle, pinning each other down before walking away. It is interesting to speculate that this ‘flocking’ behavior might help the young, inexperienced hunters capture food, even if they risk having it stolen out from under them. More eyes are more likely to find food, especially when the hunters are young and inexperienced. The sheer number of young hawks might help flush prey out, although any successful hunter will need to defend his or her dinner against the rest. Although the pond is a rich environment, the young hawks are still learning to hunt and compete for prey. A little musing: we know the hunting skills they acquire will help them procure food. Will social skills like posturing and wrestling help them acquire mates and defend territory from other red-tailed hawks?

Presumably, our hawks will spend several weeks together honing hunting, social, and other survival skills prior to dispersal (or forced eviction by adult residents). I hope the skills they have acquired through social play will help them survive.

We still don’t know how common this kind of aggregation is, although I intend to do more reading and research in the weeks to come. Is this common outside of hot spots like the Eaglecrest pond? I have no idea. More questions: we have watched young eagles and vultures play, although those birds were pre-fledging. How does pre-fledging play inform post-fledging play? How is play different and alike in different species? Do parents play with young? Why is play so prevalent in juveniles? These are worthy and important questions to ask. Even TED plays attention to the importance of play: http://www.ted.com/talks/stuart_brown_says_play_is_more_than_fun_it_s_vital.html
So get out and play! 

Peregrine Falcon Nest Box Program

Bob and falcon at Minnesota Power, Cohasset plant. 

Several of the Peregrines we watch are nesting at utilities, including Xcel Energy's Sherco, Blackdog, King, Prairie Island, and Monticello plants; Dairyland Power's Alma and Genoa plants, Minnesota Power and Light's Cohasset and Hibbard plants, Great River Energy's Elk River plant, and Alliant Energy's Cassville and Lansing plants. Our utility partners are also home to other birds, including bald eagles (Xcel Fort St. Vrain), great horned owls (Xcel Valmont), kestrels (Xcel Pawnee), and blue herons (Xcel Riverside). This isn't an accident - utilities provide an excellent home for peregrine falcons and other species of birds. A list of the sites we watch online can be found at http://www.farmyou.com/falcon_cams/index.html

The Raptor Resource Project started working with utilities in 1990, when peregrine falcon Mae was spotted at the Allen S. King plant in Oak Park Heights, Minnesota. A falconer and plant employee named Paul Simonette called Bob, who verified the sighting and asked for permission to construct and mount a nest box on a catwalk at the 400' level of the plant's stack. The site was tall, near water, inaccessible to most predators, and accessible to humans while remote from their daily activities. It was perfect!

At that time, the peregrine falcon was still highly endangered. Mae's mother MF-1 was produced by the Raptor Resource Project and released from the top of the MultiFoods building in Minneapolis in 1986. When she returned to breed in 1987, she became the first Peregrine to breed in the wild mid-continent, in the US or Canada, since the species' extirpation in the early 1960s. Mae, who hatched in 1989, was one of just 13 wild peregrines produced mid-continent that year. An awful lot of falcons have hatched since then. Here is a look at total numbers as of 2012 from the nine utility/industrial sites we watch online:

• Xcel Allen S. King plant. First year: 1990. Total young produced: 60
• Xcel Sherco. First year: 1992. Total young produced: 54
• Minnesota Power and Light, Cohasset. First year: 1993. Total young produced: 59
• Xcel Blackdog. First year: 1993. Total young produced: 56
• Dairyland Power Alma. First year: 1997. Total young produced: 55
• Dairyland Power Genoa. First year: 1998. Total young produced: 46
• Red Wing Grain. First year: 2001. Total young produced: 27
• Great River Energy. First year: 2007. Total young produced: 19
• Minnesota Power and Light, Hibbard. First year: 2008. Total young produced: 10

Xcel Energy could have said 'No'. While having a peregrine falcon on site was really cool, it was also a risk.  The company had no responsibility to provide a home for endangered species, and suppose Mae died? Any persons who bring danger or death to an endangered species can be fined up to $100,000, and the story would have been headline news. But plant manager Mike Miser said 'Yes' - he thought the peregrines were neat, plant staff were enthusiastic, and the birds provided wonderful organic pigeon control. The Utility-Peregrine Project was underway!

After the success of the Allen S. King plant, several other utilities expressed an interest in their own peregrine falcons. In addition to expanding the program at Xcel Energy, we received requests for nest boxes and or releases from Dairyland Power, Minnesota Power and Light, Wisconsin Power and Light (now Alliant Energy), MidAmerican Energy, Rochester Gas and Electric, and many more. Cargill, Red Wing Grain, and Bunge America also joined our efforts, installing nest boxes in Lake City, Minnesota, Red Wing, Minnesota, and McGregor, Iowa. A few statistics:

• The utility peregrine program has produced over 1000 young falcons in the wild. 
• At present, birds are nesting at 17 RRP/utility sites. Species include peregrine falcons, bald eagles, kestrels, great horned owls, and blue herons. An osprey pole had to be removed for bridge construction in Stillwater, Minnesota, so we are waiting to see if ospreys adopt their new pole at the Allen S. King plant. 
• I pulled a list of 473 peregrines known to have survived into adulthood. 64 of them fledged from utilities and went on to nest at other utilities, bluffs, grain elevators, bridges, and buildings.
• Peregrines have been nesting at our oldest site, the Allen S. King plant, for 23 years. 60 falcons have been produced here alone.
• Our birdcam work began in 1998, with "Mae's Internest". The cam was a sensation, and Xcel Energy's site was briefly the world's busiest corporate website according to alexa.com.

Our work with utility companies is sometimes controversial. Power lines present electrocution and collision hazards and the impact of wind turbines remains unknown. Utilities in general are not considered especially friendly to conservation. But the Utility Peregrine Program, a unique marriage of bird conservation and power production, was crucial to recovering the peregrine falcon, delisted from the Federal Endangered Species List in 1999. We've also worked with power companies on avian utility interaction issues and would like to think that our falcons are one of the reasons Xcel Energy voluntarily signed a Memorandum of Agreement with the Fish and Wildlife Service in 2002. Our partnership with utility companies has greatly benefited birds. 

Tess, the Count, and Larry the Lizard: Adventures in Symbiosis

Eaglecrest watchers might be familiar with Larry the Lizard, who periodically appears at the mouth of the Barn Owl nest, sunning and catching insects. I'm no lizard expert, but I think 'he' - we don't actually know the gender - might be a northwestern fence lizard. Larry resembles a northwestern fence lizard, lives in fence lizard range, and acts like a fence lizard.

Observers have noticed that Larry and the owls appear to have a symbiotic relationship. While barn owls prefer rodents, they will eat reptiles. However, they don't bother Larry. Is it because he eats ants and other bothersome bugs before they enter the nest? As David McDonald, Eaglecrest's owner, put it, "They look at him, but they don't bother him. He keeps ants and other bugs out of their nest."

Symbiosis has not been documented between northwestern fence lizards and barn owls, but it is known to occur between screech owls and blind snakes in the southwestern United States. Screech owls bring blind snakes - a sightless underground insect hunter that looks somewhat like a long earthworm - into their burrows, where they eat the pests that compete with nestlings for stored owl prey, as well as ants and other insects that could harm the young birds. Some people believe that the owls intentionally use the snakes as nest maids, while others believe that the snakes are dropped during the parent-chick handoff and simply find the burrow a good place to live. Fred Gehlbach, a biologist from Baylor University in Texas, found that snake-occupied screech owl nests produce more and healthier fledglings than do snake-free nests. Once the owl family leaves, the snake crawls down the tree and returns to its underground home. According to Gelbach, blind snakes are common guests of at least four owl species. The snakes we've seen slipping in and out of the nest at Eaglecrest might be performing a similar function.

So it seems at least possible that Larry and the snakes are engaged in a mutually symbiotic relationship with the owls - a relationship between individuals of different species that benefits both. The ants and other pests attracted to the nest's prey remains provide Larry with a steady diet, while the owls reap the benefits of built-in pest control. The snakes may be performing a similar function inside the owls' burrow. As scary as snakes might look to some of us (human) watchers, it is quite possible that they and the lizards are welcome guests.

Thanks to Eaglecrest for giving us a look at Larry!

---

Symbiosis may be much more common than we think. It comes in a number of different flavors, including:

• Mutualism:  a relationship between individuals of different species that benefits both.
• Commensalism: a relationship between individuals of different species in which one species benefits and the other is neither harmed nor helped.
• Parasitism: a relationship between individuals of different species in which one species benefits and the other is harmed.

We've seen all three of these at the Decorah Bald Eagle nest. I'll return to this subject in a later post. 

Things that helped me learn about this topic: 

• David McDonald, who noticed the relationship and brought it to our attention.
• When Animal Enemies Unite: http://www.nwf.org/News-and-Magazines/National-Wildlife/Animals/Archives/2010/Friends-and-enemies.aspx
• Symbiosis: http://en.wikipedia.org/wiki/Symbiosis
• Fence Lizards: http://www.californiaherps.com/lizards/pages/s.o.occidentalis.html

Turkey Vulture Musings

Some people enjoy watching the little Turkey vultures and others do not. The TVs behave quite differently from the eaglets: they spend hours a day beating each other up, don't play in a similar fashion, appear to frighten their parents (the hooligans!), and have a very unappealing diet.  They are fun to watch (if you don't mind intestinal tug-of-war) but there are not nearly as many 'awwwwwwhhh' moments. Both Bald eagles and Turkey vultures are raptors [note - I had a few of emails that pointed out this is debatable. Some experts argue that New World vultures should be placed into storks, others argue they should have their own order, Cathartiformes, and still others argue that they should be placed into raptors]. So why are their young so different? I think - and this is speculation - that the way the young birds play and interact with one another reflects their very different lifestyles as adults.

Since eagles eat live prey, they need to hunt. Since recently-killed prey has firm flesh still connected by tissue, muscle, and bone, they need to tear food. When Mom and Dad bring food in, the eaglets sometimes stalk it. Once the eaglets can stand and walk well, they also tear food with their feet, steal it from their parents and one another, and mantle to guard and protect it. Food play includes stalking, pouncing, and grabbing. A few examples:      

• Decorah Eaglet Escapes and Attacks the Prey: http://youtu.be/NTu-hlvDMio
• Food Play: http://youtu.be/Dl_j01QLCkg
• Tug of War with Mom: http://youtu.be/tueVfFb0W6M

Turkey vultures, on the other hand, eat primarily dead food (they have been observed eating pumpkins), detectable by the smell of ethyl mercaptan.  They don't need to stalk or hunt wary prey, although they do need to eat quickly to compete with other vultures and carrion eaters, including larger Black and King vultures. I don't know that carrion or hunks of carrion could be carried to the nest without falling apart: at any rate, Turkey vultures rely entirely on regurgitation. The young don't play with food much at all that we've seen: their parents regurgitate it, they eat it, and that settles it. As John Carton noted, the chicks learn to "gulp their food properly" in response to their parents' quick in and out feedings. Eating quickly is a necessary survival skill for turkey vultures, and they don't play with their food.

• Missouri TVs, feeding and fighting: http://youtu.be/XCZUXf__y2c
• A tug of war with some intestines: http://youtu.be/fShidqNXY-U
• Trying to eat at the same time, almost mow parents over: http://youtu.be/zJgKML7gSN8

Eagles build huge nests, and the young eaglets mimic Mom and Dad's nest-building activity from a very early age. They move and place sticks and other nesting material, and play tug-of-war as well (perhaps preparing for the inevitable adult differences over where, exactly, that stick should go).

• Decorah Eagles: Hop, stick and jump! http://youtu.be/8DSnyEv2qBE
• E practices skills: http://youtu.be/welz2KgxB-g
• Nestoration: http://youtu.be/_0viodXxKtg

Turkey vultures don't build nests the way that eagles do. In this case, the adults spent some time preparing the straw prior to egg-laying: they pecked at objects, snapped straw into smaller pieces, and formed a depression for their eggs.  However, they invested very little time in maintaining, building, or caring for it once the eggs were laid. While the young turkey vultures roam around and explore objects, they don't engage in the same kind of stick and nesting material play that the eaglets do. In this case, no nest seems to equal no nesting play.

Turkey vultures and Bald eagles are both social, and both sets of young spend a lot of time interacting with one another. When it comes to play, the eaglets tussle, cuddle, preen, steal food, and play tug of war. The young vultures (vulturelets?) beat each other relentessly, with occasional breaks for preening. While the eaglets appear to play at the complex skills of hunting, nest building, and competing for food, the young vultures appear to play primarily at competition, period. Although Turkey vultures are social, this behavior leads me to wonder about the intensity of TV to TV food competition. Is this all about other carrion eaters, or do adult Turkey vultures beat each other up over food as well?

• Turkey Vulture parents feeding, babies fighting: http://youtu.be/7Q5L77jxaEo
• Missouri TVs fighting: http://youtu.be/l9MMTSqpeN8
• Missouri Turkey vulture chicks fight: http://youtu.be/M2WrnZsH24c

Although the behavior of the little Turkey vultures may not be as appealing as the eaglets to human watchers, their play and interaction is equally effective at helping to prepare them for the challenges of adult life. John predicts that they will most likely begin flying between August 28 and September 3rd. I've enjoyed watching them in the nest and look forward to his observations once they have left.

If you haven't watched the Turkey vultures, you can see them at: http://www.ustream.tv/missouriturkeyvultures

Watching Bald Eagles

Bob took a turn operating the controls at the Bald eagle camera this morning. He was fascinated by Dad, who brought in three suckers in one hour. Suckerfish are 'rough' fish: generally considered undesirable by humans, they have large scales, fleshy lips, and a 'sucker' mouth that is wonderful for attaching to rocks and scouring river bottoms for food. They spawn in shallow water during the spring, when water temperatures reach between 47 and 60 degrees Fahrenheit. The Iowa DNR tells us that males move upstream in large schools, congregating and defending spawning territories that contain gravel riffles and rubble shoals. While suckers are spawning, eagles are raising a family. Suckers make easy prey: they are relatively exposed, there are a lot of them, they congregate in one area, and they don't leave until spawning is done. "Think about it," Bob said. "We are watching them eat food they evolved with over eons."

Bald eagles have several excellent adaptations for fishing. An eagle's powerful toes, locking talons, and spicules - tiny projections on the bottom of its feet - help it grasp and hold slippery fish, as do the serrations on the roof of its mouth. The black pigment on its wing feathers strengthens them against breakage when it dives into the water. Its nictitating membrane and the boney ridge over its eyes - so noticeable in Mom - helps protect its eyes from sunlight and reduces glare. Bald eagles eat a wide variety of prey, but they are fishers par excellence.

So how old are Bald eagles as a species? Birds begin to appear in the fossil record between 144 and 66 million years ago. These ancestral birds gradually diverged into separate species. Kites, the ancestors of today's Acciptiridae, emerged tens of millions of years ago. Like modern eagles (but not all Acciptiridae) they are believed to have scavenged and hunted fish. The first eagles descended from kites roughly 36 million years ago, and the earliest known fossil remains that closely resemble the bald eagle date back to about a million years ago.

Plio-pleistocene Bald eagles in North America might have shared the landscape with mammoths, dolichohippine horses, camelops, glyptotherium, terror birds, and stegomastodon, as well as more familiar bats, birds, rodents, and fish. Did they build the same kinds of nests? Did they raise their young the same way? Did eagles feed on suckerfish even back then? We don't know: birds don't preserve very well. Still, the thought that Bald eagles flew over an ice-age North America gives me the shivers. So much of what was is gone now, but eagles and sucker fish are still with us.

Fast-forward to a shallow stream 15,000 years ago. Suckers are making their way upstream to spawn. Suddenly, an eagle swoops down and hooks one to bring to its waiting young, who are clamoring hungrily in the nest above. Dad has food. His legacy will survive into a future he can't imagine.

---

Things that helped me learn and write about this topic:

• Personal communication, Bob Anderson
• http://www.ncbi.nlm.nih.gov/pubmed/19241464 (Plio-pleistocene eagle predation)
• http://www.profleeberger.com/files/Berger_further_evidence_taung_main_article.pdf (Plio-pleistocene eagle predation)
• http://si-pddr.si.edu/jspui/bitstream/10088/7069/1/James-05-Auk-Paleogene_birds.pdf (Paeogene fossils and the radiation of modern birds)
• http://www.iowadnr.gov/Fishing/IowaFishSpecies/FishDetails.aspx?SpeciesCode=SHR (Iowa DNR, suckerfish)
• http://tinyurl.com/7q8u99d (Fauna of Pleistocene North America)
• http://www.eagles.org/vu-study/biology/structure-and-anatomy.php (eagle adaptations)
• http://www.pbs.org/wnet/nature/episodes/american-eagle/bald-eagles-evolutionary-ancestors/4274/ (eagle adaptations and evolutionary history. Much of this information came from the book THE BALD EAGLE, by Stalmaster, Mark V. 1987, published by University Books, New York.)
• http://bss.sfsu.edu/holzman/courses/Fall02%20projects/bald%20eagle.html  (bald eagle evolutionary history). Nice job, Michael Rochelle!

It was fun to read about plio-pleistocene life forms. It reminded me of very loved books from my childhood that I haven't thought about in ages: brightly colored children's science books about the ice age with fantastic illustrations of mammoths, saber-tooth tigers, and so much more. What a treat to think of them again!